Planetary Hour Calculator

Classical Chaldean planetary hours for any date and location — calculated entirely in your browser

Zero Upload — location stays in your browser

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About Planetary Hours

What Is a Planetary Hour?

A planetary hour divides each day into 24 unequal segments: 12 from sunrise to sunset, 12 from sunset to the next sunrise. Each segment is governed by one of the seven classical planets in Chaldean order. The length adapts to the season — long in summer, short in winter.

Wikipedia: Planetary Hours

The Chaldean Order

The Chaldean order (Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon) reflects classical geocentric distances of the planets. The sequence repeats endlessly through the 24 hours, connecting each segment to a cosmic influence recognized since ancient Mesopotamia.

Britannica: History of Astrology

Day Rulers & Day Names

The first daylight hour of each day names that day: Sunday is ruled by the Sun, Monday by the Moon, Tuesday by Mars, Wednesday by Mercury, Thursday by Jupiter, Friday by Venus, Saturday by Saturn. This naming system spans Indo-European and Semitic calendars worldwide.

Agrippa: Occult Philosophy

Sunrise / Sunset Algorithm

Planetary hour boundaries depend on precise local sunrise and sunset times. This calculator uses Jean Meeus's Chapter 25 simplified solar algorithm (±1 minute accuracy), the same formulas used in professional ephemeris software and validated against USNO data.

USNO Solar Position Data

Frequently Asked Questions

What are planetary hours used for?
Planetary hours are used in classical astrology, ceremonial magic, and Hermetic tradition to select auspicious times for activities aligned with specific planetary energies. For example, a Venus hour is considered ideal for matters of love and beauty; a Mercury hour for communication and study.
How are planetary hours calculated?
The daylight period (sunrise to sunset) is divided into 12 equal parts and the night (sunset to next sunrise) into 12 equal parts. The first daylight hour is assigned to the day ruler (Sun on Sunday, Moon on Monday, and so on), with subsequent hours following the Chaldean order: Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon → repeat.
Why does my location matter?
Planetary hours are based on your local sunrise and sunset times, which vary by latitude and longitude. The same calendar date yields completely different schedules in New York versus Tokyo. Your coordinates are used only for the calculation and never leave your browser.
What happens at polar latitudes?
Above approximately 66.5° latitude during extreme seasons, the sun may not rise or set (polar day or night). No valid planetary hour schedule can be computed in that case, and the calculator displays a POLAR_REGION error. Try a nearby lower-latitude location or a different date.

Calculate planetary hours for any date and location. Find today's chaldean planetary hours, current ruling planet, and 24-hour schedule. No data uploaded — runs entirely in your browser. · All calculations execute client-side using Jean Meeus Chapter 25 solar algorithm — zero network requests, zero data transmitted.